On the “Impossible-ness”of our goal

On the Impossible -ness of our goal: what if our goal is not possible physically? meaning, if I need to lose 130 lbs , that would mean I would need to lose 2.5 lbs WITHOUT FAIL EACH WEEK. I don’t think that is possible because bodies don’t work that way, sometimes the wt loss is irregular and I believe say one could maybe lose 80-100 lbs. But, I need to lose more than that! That doesn’t mean I will not dedicate myself to making this goal happen in 2018 by myself by doing all the elements ( worthy fails) that would go into making this goal happen if it Were possible, I intend to! Should I just proceed as AS IF losing 130 lbs in one year IS possible ? Or, should I make the goal 100 because that’s a big goal to and in the past I haven’t been able to achieve it? Thanks.